Sauna bathing is associated with reduced cardiovascular mortality and improves risk prediction in men and women: a prospective cohort study.
Level 3 - non-randomized controlled study
Prospective cohort study with long-term follow-up
PubMed 30486813 · doi:10.1186/s12916-018-1198-0
What was done
Sauna bathing habits were assessed at baseline in a prospective cohort of 1,688 participants (mean age 63 years, range 53–74; 51.4% women). Fatal cardiovascular disease (CVD) events were recorded over a median follow-up of 15.0 years (interquartile range, 14.1–15.9). Multivariable hazard ratios (HRs) for CVD mortality were calculated for weekly sauna sessions (2–3 and 4–7 sessions/week compared with 1 session/week) and duration (minutes/week), adjusting for established CVD risk factors, physical activity, socioeconomic status, and incident coronary heart disease. Incremental risk prediction was assessed by C-index change, difference in -2 log likelihood, and categorical net reclassification improvement.
What was found
A total of 181 fatal CVD events occurred during follow-up. In multivariable-adjusted models, compared with participants having 1 session per week, HRs for CVD mortality were 0.75 (95% CI, 0.52 to 1.08) for 2–3 sessions per week and 0.23 (95% CI, 0.08 to 0.65) for 4–7 sessions per week. Duration of sauna use per week was inversely associated with CVD mortality in a continuous manner. Adding sauna frequency to conventional risk prediction models improved the C-index by 0.0091 (P = 0.010), -2 log likelihood (P = 0.019), and net reclassification by 4.14% (P = 0.004).
Why it matters
This study shows that frequent sauna bathing is strongly associated with lower cardiovascular mortality in both women and men, extending previous findings from male-only cohorts and improving long-term CVD risk prediction models.
Limits
The study is observational and cannot establish causality; residual confounding from general health status or healthy user effects may persist. Sauna exposure was assessed only at baseline, allowing potential misclassification over the 15-year follow-up. Findings from this middle-aged to elderly Finnish cohort may not generalize to populations with different baseline sauna habits or cardiovascular risk profiles.
Cited by
- supports Regular sauna bathing several times per week significantly reduces the incidence of heart disease in Finnish men.